Request routing based on class

ABSTRACT

A system and method for management and processing of resource requests is provided. A content delivery network service provider receives a DNS query from a client computing device. The DNS query corresponds to a requested resource from the client computing device. The content delivery network service provider associates the client computing device with a cluster of other client computing devices. Based on routing information for the cluster, the content delivery network service provider routes the DNS query. The process can further include monitoring performance data associated with the delivery of the requested resource and updating the routing information for the cluster based on the performance data for use in processing subsequent requests from client computing devices in the cluster.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/405,779, now U.S. Pat. No. 10,797,995, entitled “REQUEST ROUTINGBASED ON CLASS” and filed May 7, 2019, which in turn is a continuationof U.S. patent application Ser. No. 15/888,860, now U.S. Pat. No.10,305,797, entitled “REQUEST ROUTING BASED ON CLASS” and filed Feb. 5,2018, which in turn is a continuation of U.S. patent application Ser.No. 15/408,362, now U.S. Pat. No. 9,887,915, entitled “REQUEST ROUTINGBASED ON CLASS” and filed Jan. 17, 2017, which in turn is a continuationof U.S. patent application Ser. No. 14/263,824, now U.S. Pat. No.9,571,389, entitled “REQUEST ROUTING BASED ON CLASS” and filed Apr. 28,2014, which in turn is a continuation of U.S. patent application Ser.No. 13/766,574, now U.S. Pat. No. 8,713,156, entitled “REQUEST ROUTINGBASED ON CLASS” and filed Feb. 13, 2013, which in turn is a continuationof U.S. patent application Ser. No. 13/418,239, now U.S. Pat. No.8,386,596, entitled “REQUEST ROUTING BASED ON CLASS” and filed Mar. 12,2012, which in turn is a continuation of U.S. patent application Ser.No. 13/098,366, now U.S. Pat. No. 8,135,820, entitled “REQUEST ROUTINGBASED ON CLASS” and filed Apr. 29, 2011, which in turn is a continuationof U.S. patent application Ser. No. 12/060,173, now U.S. Pat. No.7,962,597, entitled “REQUEST ROUTING BASED ON CLASS” and filed Mar. 31,2008, the disclosures of which are incorporated herein by reference.

BACKGROUND

Generally described, computing devices and communication networks can beutilized to exchange information. In a common application, a computingdevice can request content from another computing device via thecommunication network. For example, a user at a personal computingdevice can utilize a software browser application to request a Web pagefrom a server computing device via the Internet. In such embodiments,the user computing device can be referred to as a client computingdevice and the server computing device can be referred to as a contentprovider.

Content providers are generally motivated to provide requested contentto client computing devices often with consideration of efficienttransmission of the requested content to the client computing deviceand/or consideration of a cost associated with the transmission of thecontent. For larger scale implementations, a content provider mayreceive content requests from a high volume of client computing deviceswhich can place a strain on the content provider's computing resources.Additionally, the content requested by the client computing devices mayhave a number of components, which can further place additional strainon the content provider's computing resources.

With reference to an illustrative example, a requested Web page, ororiginal content, may be associated with a number of additionalresources, such as images or videos, which are to be displayed with theWeb page. In one specific embodiment, the additional resources of theWeb page are identified by a number of embedded resource identifiers,such as uniform resource locators (“URLs”). In turn, software on theclient computing devices typically processes embedded resourceidentifiers to generate requests for the content. Often, the resourceidentifiers associated with the embedded resources reference a computingdevice associated with the content provider such that the clientcomputing device would transmit the request for the additional resourcesto the referenced content provider computing device. Accordingly, inorder to satisfy a content request, the content provider would provideclient computing devices data associated with the Web page as well asthe data associated with the embedded resources.

Some content providers attempt to facilitate the delivery of requestedcontent, such as Web pages and/or resources identified in Web pages,through the utilization of a content delivery network (“CDN”) serviceprovider. A CDN server provider typically maintains a number ofcomputing devices in a communication network that can maintain contentfrom various content providers. In turn, content providers can instruct,or otherwise suggest to, client computing devices to request some, orall, of the content provider's content from the CDN service provider'scomputing devices.

As with content providers, CDN service providers are also generallymotivated to provide requested content to client computing devices oftenwith consideration of efficient transmission of the requested content tothe client computing device and/or consideration of a cost associatedwith the transmission of the content. Accordingly, CDN service providersoften consider factors such as latency of delivery of requested contentin order to meet service level agreements or to generally improve thequality of delivery service.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a block diagram illustrative of content delivery environmentincluding a number of client computing devices, content provider, and acontent delivery network service provider;

FIG. 2 is a block diagram of the content delivery environment of FIG. 1illustrating the registration of a content provider with a contentdelivery service provider;

FIG. 3 is a block diagram of the content delivery environment of FIG. 1illustrating the generation and processing of a content request from aclient computing device to a content provider;

FIG. 4 is a block diagram of the content delivery environment of FIG. 1illustrating one embodiment of the generation and processing of a DNSquery corresponding to an embedded resource from a client computingdevice to a content delivery network service provider;

FIGS. 5A-5C are block diagrams of the content delivery environment ofFIG. 1 illustrating another embodiment of the generation and processingof a DNS query corresponding to an embedded resource from a clientcomputing device to a content delivery network service provider and thesubsequent generation and processing of DNS queries corresponding to afirst and a second alternative resource identifier from a clientcomputing device to a content delivery network;

FIG. 6 is a block diagram of the content delivery environment of FIG. 1illustrating the generation and processing of embedded resource requestsfrom a client computing device to a content delivery network serviceprovider;

FIG. 7 is a flow diagram illustrative of a request routing routineimplemented by a content delivery network service provider for selectinga cache server component; and

FIG. 8 is a flow diagram illustrative a request routing routineimplemented by a content delivery network service provider for updatingrouting information.

DETAILED DESCRIPTION

Generally described, the present disclosure is directed to themanagement and processing of resource requests made to a contentdelivery network (“CDN”) service provider from client computing devices.Specifically, aspects of the disclosure will be described with regard torouting information associated with a resource request based on routinginformation for a cluster of client computing devices. Although variousaspects of the disclosure will be described with regard to illustrativeexamples and embodiments, one skilled in the art will appreciate thatthe disclosed embodiments and examples should not be construed aslimiting.

FIG. 1 is a block diagram illustrative of content delivery environment100 for the management and processing of content requests. Asillustrated in FIG. 1, the content delivery environment 100 includes anumber of client computing devices 102 (generally referred to asclients) for requesting content from a content provider and/or a CDNservice provider. In an illustrative embodiment, the client computingdevices 102 can correspond to a wide variety of computing devicesincluding personal computing devices, laptop computing devices,hand-held computing devices, terminal computing devices, mobile devices,wireless devices, various electronic devices and appliances and thelike. In an illustrative embodiment, the client computing devices 102include necessary hardware and software components for establishingcommunications over a communication network 108, such as a wide areanetwork or local area network. For example, the client computing devices102 may be equipped with networking equipment and browser softwareapplications that facilitate communications via the Internet or anintranet.

Although not illustrated in FIG. 1, each client computing device 102utilizes some type of local DNS resolver component, such as a DNS Nameserver, that generates the DNS queries attributed to the clientcomputing device. In one embodiment, the local DNS resolver componentmay be provide by an enterprise network to which the client computingdevice 102 belongs. In another embodiment, the local DNS resolvercomponent may be provided by an Internet Service Provider (ISP) thatprovides the communication network connection to the client computingdevice 102.

The content delivery environment 100 can also include a content provider104 in communication with the one or more client computing devices 102via the communication network 108. The content provider 104 illustratedin FIG. 1 corresponds to a logical association of one or more computingdevices associated with a content provider. Specifically, the contentprovider 104 can include a web server component 110 corresponding to oneor more server computing devices for obtaining and processing requestsfor content (such as Web pages) from the client computing devices 102.The content provider 104 can further include an origin server component112 and associated storage component 114 corresponding to one or morecomputing devices for obtaining and processing requests for networkresources from the CDN service provider. One skilled in the relevant artwill appreciate that the content provider 104 can be associated withvarious additional computing resources, such additional computingdevices for administration of content and resources, DNS name servers,and the like. For example, although not illustrated in FIG. 1, thecontent provider 104 can be associated with one or more DNS name servercomponents that would be authoritative to resolve client computingdevice DNS queries corresponding to a domain of the content provider.

With continued reference to FIG. 1, the content delivery environment 100can further include a CDN service provider 106 in communication with theone or more client computing devices 102 and the content providers 104via the communication network 108. The CDN service provider 106illustrated in FIG. 1 corresponds to a logical association of one ormore computing devices associated with a CDN service provider.Specifically, the CDN service provider 106 can include a number of Pointof Presence (“POP”) locations 116, 122, 128 that correspond to nodes onthe communication network 108. Each POP 116, 122, 128 includes a DNScomponent 118, 124, 130 made up of a number of DNS server computingdevices for resolving DNS queries from the client computers 102. EachPOP 116, 122, 128 also includes a resource cache component 120, 126, 132made up of a number of cache server computing devices for storingresources from content providers and transmitting various requestedresources to various client computers. The DNS components 118, 124 and130 and the resource cache components 120, 126 132 may further includeadditional software and/or hardware components that facilitatecommunications including, but not limited, load balancing or loadsharing software/hardware components.

In an illustrative embodiment, the DNS component 118, 124, 130 andresource cache component 120, 126, 132 are considered to be logicallygrouped, regardless of whether the components, or portions of thecomponents, are physically separate. Additionally, although the POPs116, 122, 128 are illustrated in FIG. 1 as logically associated with theCDN service provider 106, the POPs will be geographically distributedthroughout the communication network 108 in a manner to best servevarious demographics of client computing devices 102. Additionally, oneskilled in the relevant art will appreciate that the CDN serviceprovider 106 can be associated with various additional computingresources, such additional computing devices for administration ofcontent and resources, and the like.

One skilled in the relevant art will appreciate that the components andconfigurations provided in FIG. 1 are illustrative in nature.Accordingly, additional or alternative components and/or configurations,especially regarding the additional components, systems and subsystemsfor facilitating communications may be utilized.

With reference now to FIGS. 2-6, the interaction between variouscomponents of the content delivery environment 100 of FIG. 1 will beillustrated. For purposes of the example, however, the illustration hasbeen simplified such that many of the components utilized to facilitatecommunications are not shown. One skilled in the relevant art willappreciate that such components can be utilized and that additionalinteractions would accordingly occur without departing from the spiritand scope of the present disclosure.

With reference to FIG. 2, an illustrative interaction for registrationof a content provider 104 with the CDN service provider 106 will bedescribed. As illustrated in FIG. 2, the CDN content registrationprocess begins with registration of the content provider 104 with theCDN service provider 106. In an illustrative embodiment, the contentprovider 104 utilizes a registration application program interface(“API”) to register with the CDN service provider 106 such that the CDNservice provider 106 can provide content on behalf of the contentprovider 104. The registration API includes the identification of theorigin server 112 of the content provider 104 that will providerequested resources to the CDN service provider 106.

One skilled in the relevant art will appreciate that upon identificationof appropriate origin servers 112, the content provider 104 can begin todirect requests for content from client computing devices 102 to the CDNservice provider 106. Specifically, in accordance with DNS routingprinciples, a client computing device request corresponding to aresource identifier would eventually be directed toward a POP 116, 122,128 associated with the CDN service provider 106. In the event that theresource cache component 120, 126, 132 of a selected POP does not have acopy of a resource requested by a client computing device 102, theresource cache component will request the resource from the originserver 112 previously registered by the content provider 104.

With continued reference to FIG. 2, upon receiving the registration API,the CDN service provider 106 obtains and processes the registrationinformation. In an illustrative embodiment, the CDN service provider 106can then generate additional information that will be used by the clientcomputing devices 102 as part of the content requests. The additionalinformation can include, without limitation, client identifiers, such asclient identification codes, content provider identifiers, such ascontent provider identification codes, executable code for processingresource identifiers, such as script-based instructions, and the like.One skilled in the relevant art will appreciate that various types ofadditional information may be generated by the CDN service provider 106and that the additional information may be embodied in any one of avariety of formats.

The CDN service provider 106 returns an identification of applicabledomains for the CDN service provider (unless it has been previouslyprovided) and any additional information to the content provider 104. Inturn, the content provider 104 can then process the stored content withcontent provider specific information. In one example, as illustrated inFIG. 2, the content provider 104 translates resource identifiersoriginally directed toward a domain of the origin server 112 to a domaincorresponding to the CDN service provider. The translated URLs areembedded into requested content in a manner such that DNS queries forthe translated URLs will resolve to a DNS server corresponding to theCDN service provider 106 and not a DNS server corresponding to thecontent provider 104. Although the translation process is illustrated inFIG. 2, in some embodiments, the translation process may be omitted in amanner described in greater detail below.

Generally, the identification of the resources originally directed tothe content provider 104 will be in the form of a resource identifierthat can be processed by the client computing device 102, such asthrough a browser software application. In an illustrative embodiment,the resource identifiers can be in the form of a uniform resourcelocator (“URL”). Because the resource identifiers are included in therequested content directed to the content provider, the resourceidentifiers can be referred to generally as the “content provider URL.”For purposes of an illustrative example, the content provider URL canidentify a domain of the content provider 104 (e.g.,contentprovider.com), a name of the resource to be requested (e.g.,“resource.xxx”) and a path where the resource will be found (e.g.,“path”). In this illustrative example, the content provider URL has theform of:

-   -   http://www.contentprovider.com/path/resource.xxx

During an illustrative translation process, the content provider URL ismodified such that requests for the resources associated with thetranslated URLs resolve to a POP associated with the CDN serviceprovider 106. In one embodiment, the translated URL identifies thedomain of the CDN service provider 106 (e.g., “cdnprovider.com”), thesame name of the resource to be requested (e.g., “resource.xxx”) and thesame path where the resource will be found (e.g., “path”). Additionally,the translated URL can include additional processing information (e.g.,“additional information”). The translated URL would have the form of:

-   -   http://additionalinformation.cdnprovider.com/path/resources.xxx

In another embodiment, the information associated with the CDN serviceprovider 106 is included in the modified URL, such as through prependingor other techniques, such that the translated URL can maintain all ofthe information associated with the original URL. In this embodiment,the translated URL would have the form of:

-   -   http://additionalinformation.cdnprovider.com/www.contentprovider.com/path/resource.xxx

With reference now to FIG. 3, after completion of the registration andtranslation processes illustrated in FIG. 2, a client computing device102 subsequently generates a content request that is received andprocessed by the content provider 104, such as through the Web server110. In accordance with an illustrative embodiment, the request forcontent can be in accordance with common network protocols, such as thehypertext transfer protocol (“HTTP”). Upon receipt of the contentrequest, the content provider 104 identifies the appropriate responsivecontent. In an illustrative embodiment, the requested content cancorrespond to a Web page that is displayed on the client computingdevice 102 via the processing of information, such as hypertext markuplanguage (“HTML”), extensible markup language (“XML”), and the like. Therequested content can also include a number of embedded resourceidentifiers, described above, that corresponds to resource objects thatshould be obtained by the client computing device 102 as part of theprocessing of the requested content. The embedded resource identifierscan be generally referred to as original resource identifiers ororiginal URLs.

Upon receipt of the requested content, the client computing device 102,such as through a browser software application, begins processing any ofthe markup code included in the content and attempts to acquire theresources identified by the embedded resource identifiers. Accordingly,the first step in acquiring the content corresponds to the issuance, bythe client computing device 102 (through its local DNS resolver), of aDNS query for the Original URL resource identifier that results in theidentification of a DNS server authoritative to the “.” and the “com”portions of the translated URL. After resolving the “.” and “com”portions of the embedded URL, the client computing device 102 thenissues a DNS query for the resource URL that results in theidentification of a DNS server authoritative to the “cdnprovider”portion of the embedded URL. The issuance of DNS queries correspondingto the “.” and the “com” portions of a URL are well known and have notbeen illustrated.

With reference now to FIG. 4, in an illustrative embodiment, thesuccessful resolution of the “cdnprovider” portion of the original URLidentifies a network address, such as an IP address, of a DNS serverassociated with the CDN service provider 106. In one embodiment, the IPaddress can be a specific network address unique to a DNS servercomponent of a POP. In another embodiment, the IP address can be sharedby one or more POPs. In this embodiment, a further DNS query to theshared IP address utilizes a one-to-many network routing schema, such asanycast, such that a specific POP will receive the request as a functionof network topology. For example, in an anycast implementation, a DNSquery issued by a client computing device 102 to a shared IP addresswill arrive at a DNS server component logically having the shortestnetwork topology distance, often referred to as network hops, from theclient computing device. The network topology distance does notnecessarily correspond to geographic distance. However, in someembodiments, the network topology distance can be inferred to be theshortest network distance between a client computing device 102 and aPOP.

With continued reference to FIG. 4, in either of the above identifiedembodiments (or any other embodiment), a specific DNS server in the DNScomponent 118 of a POP 116 receives the DNS query corresponding to theoriginal URL from the client computing device 102. Once one of the DNSservers in the DNS component 118 receives the request, the specific DNSserver attempts to resolve the request. In one illustrative embodimentas shown in FIG. 4, a specific DNS server resolves the DNS query byidentifying an IP address of a cache server component that will processthe request for the requested resource. As described above and as willbe described further below in reference to FIG. 6, a selected resourcecache component can process the request by either providing therequested resource if it is available or attempt to obtain the requestedresource from another source, such as a peer cache server computingdevice or the origin server 112 of the content provider 104.

In further reference to FIG. 4, the specific DNS server can utilize avariety of information in selecting a resource cache component. In anillustrative embodiment, and as will be further described below inreference to FIGS. 7 and 8, the DNS server determines a class associatedwith the requesting client computing device. For example, the class cancorrespond to a specific geographic region to which the client computingdevice belongs or an internet service provider for the client computingdevice. Such class information can be determined from the clientdirectly (such as information provided by the client computing device orISP) or indirectly (such as inferred through a client computing device'sIP address). Based on the class, the DNS server determines appropriaterouting information. Then, for embodiments described specifically inreference to FIG. 4, the DNS server selects an appropriate resourcecache component for providing content associated with the resourcerequest based on the routing information for the determined class of theclient computing device. The IP address selected by the DNS server maycorrespond to a specific caching server in the resource cache.Alternatively, the IP address can correspond to a hardware/softwareselection component (such as a load balancer). As will also be furtherdescribed below, the DNS server can further utilize network performancemeasurements to assist in selecting specific resource cache componentsfor the determined class.

With reference now to FIGS. 5A-5C, as an alternative to selecting aresource cache component upon receipt of a DNS query as described inreference to FIG. 4, the CDN service provider 106 can maintain sets ofvarious alternative resource identifiers. The alternative resourceidentifiers can be provided by the CDN service provider 106 to theclient computing device 102 such that a subsequent DNS query on thealternative resource identifier will resolve to a different DNS servercomponent within the CDN service provider's network. In an illustrativeembodiment, the alternative resource identifiers are in the form of oneor more canonical name (“CNAME”) records. In one embodiment, each CNAMErecord identifies a domain of the CDN service provider 106 (e.g.,“cdnprovider.com” or “cdnprovider-1.com”). As will be explained ingreater detail below, the domain in the CNAME does not need to be thesame domain found in original URL or in a previous CNAME record.Additionally, each CNAME record includes additional information, such asrequest routing information, (e.g., “request routing information”). Anillustrative CNAME record can have the form of:

-   -   http://request_routing_information.cdnprovider.com

In an illustrative embodiment, the CNAME records are generated andprovided by the DNS servers to identify a more appropriate DNS server ofthe CDN service provider 106. As with selecting an appropriate resourcecache component as described above in reference to FIG. 4, the DNSserver receiving the initial DNS query can utilize a variety ofinformation to select a more appropriate DNS server of the CDN serviceprovider 106 to resolve the resource request. In an illustrativeembodiment, and as will also be further described below in reference toFIGS. 7 and 8, the DNS server determines a class associated with therequesting client computing device. Again, the class can, for example,correspond to a specific geographic region to which the client computingdevice belongs or an internet service provider for the client computingdevice. In any case, the DNS server may obtain class information fromthe client directly (such as information provided by the clientcomputing device or ISP) or indirectly (such as inferred through aclient computing device's IP address). Based on the class, the DNSserver determines appropriate routing information. Then, for theembodiments described specifically in reference to FIG. 5A, the DNSserver selects an appropriate alternative DNS server for use inresolving the resource request based on the routing information for thedetermined class of the client computing device. As will also be furtherdescribed below, the DNS server can further utilize network performancemeasurements to select specific alternative DNS servers for thedetermined class.

In accordance with an illustrative embodiment, the DNS server maintainsa data store that defines CNAME records for various original URLs. If aDNS query corresponding to a particular original URL matches an entry inthe data store, the DNS server returns a CNAME record as defined in thedata store. In an illustrative embodiment, the data store can includemultiple CNAME records corresponding to a particular original URL. Themultiple CNAME records would define a set of potential candidates thatcan be returned to the client computing device. In such an embodiment,the DNS server, either directly or via a network-based service, selectsone of the CNAME records defined in the data store as more appropriaterouting information based on logic that factors a determined class ofthe requesting client computing device. It will be appreciated by oneskilled in the art and others that the DNS server can implement furtheradditional logic in selecting an appropriate CNAME from a set ofpossible of CNAMEs. In an illustrative embodiment, each DNS servercomponent 118, 124, 130 maintains the same data stores that define CNAMErecords, which can be managed centrally by the CDN service provider 106.Alternatively, each DNS server component 118, 124, 130 can have POPspecific data stores that define CNAME records, which can be managedcentrally by the CDN service provider 106 or locally at the POP 116,122, 128. Still further, each DNS server computing device within the DNSserver components 118, 124, 130 can utilize shared data stores managedby a respective POP or a local data store specific to an individual DNSserver computing device.

The returned CNAME can also include request routing information that isdifferent from or in addition to the information provided in URL/CNAMEof the current DNS query. For example, if the CNAME selection is basedon a class associated with the requesting client computing device, aspecific class can be identified in the “request_routing_information”portion of the specific CNAME record. A similar approach could be takento identify service level plans and file management by including aspecific identifier in the “request_routing_information” portion of theCNAME record. In another embodiment, request routing information can befound in the identification of a CDN service provider 106 domaindifferent from the domain found in the current URL/CNAME. For example,if the CNAME is based on a regional plan, a specific regional plandomain (e.g., “cdnprovider-region1.com”) could be used in the domainname portion of the specific CNAME record. Any additional requestrouting information can be prepended to the existing request routinginformation in the current URL/CNAME such that the previous requestrouting information would not be lost (e.g.,http://serviceplan.regionalplan.cdnprovider.com). One skilled in therelevant art will appreciate that additional or alternative techniquesand/or combination of techniques may be used to include the additionalrequest routing information in the CNAME record that is selected by theDNS server component 118.

With continued reference to FIG. 5A, one skilled in the relevant artwill appreciate that the DNS server may select (or otherwise obtain) aCNAME record that is intended to resolve to a more appropriate DNSserver of the CDN service provider 106. It may be possible, however,that the same DNS server would also be authoritative for the subsequentDNS query for the CNAME to be provided to the client computing device.For example, a specific DNS server may be authoritative for both aspecific regional plan and a service level plan. Thus, returning a CNAMEwould still result in the DNS query arriving at the same DNS query(which may also be due in part to the client computing device'sgeography). In such an embodiment, the DNS server, such as DNS servercomponent 118, may choose to resolve the future DNS query in advance.

With reference now to FIG. 5B, upon receipt of the CNAME from the DNSserver component 118, the client computing device 102 generates asubsequent DNS query corresponding to the CNAME. As previously discussedwith regard to FIG. 4, the DNS query process could first start with DNSqueries for the “.” and “com” portions, followed by a query for the“cdnprovider” portion of the CNAME. To the extent, however, that theresults of a previous DNS queries can be cached (and remain valid), theclient computing device 102 can utilize the cached information and doesnot need to repeat the entire process. However, at some point, dependingon whether the CNAME provided by DNS server component 118 (FIG. 5A) andthe previous URL/CNAME share common CDN service provider domains, thecurrent CNAME DNS query resolves to a different POP provided by the CDNservice provider 106. As illustrated in FIG. 5B, the DNS servercomponent 124 of POP 122 receives the current CNAME based on thedifferent information in the current CNAME previously provided by theDNS server component 118. As previously described, the DNS servercomponent 124 can then determine whether to resolve the DNS query on theCNAME with an IP address of a cache component that will process thecontent request or whether to provide another alternative resourceidentifier selected in the manners described above.

For purposes of illustration, assume that the DNS server component 118determines that the DNS query corresponding to the current CNAME(provided by DNS server component 116) also corresponds to a CNAMErecord in its data store. In such an example, the DNS server component124 would do any necessary processing to select a specific CNAME asdescribed above and return the CNAME to the client computing device.With reference now to FIG. 5C, the client computing device 102 would nowtransmit a second subsequent DNS query corresponding to the CNAMEprovided by DNS server component 124 (FIG. 5B). In accordance with DNSquery processes already described, the DNS query would illustratively bereceived by the DNS server component 130 of POP 128. Again, the DNSserver component 130 can then determine whether to resolve the DNS queryon the CNAME with an IP address of a cache component that will processthe content request or whether to provide another alternative resourceidentifier selected in the manners described above. In this example, theDNS server component 130 returns an IP address.

With continued reference to FIG. 5C, in an illustrative embodiment, theDNS server components, such as DNS server component 130, can utilize avariety of information in selecting a resource cache component. In oneexample, the DNS server component can default to a selection of aresource cache component of the same POP. In another example, the DNSserver components can select a resource cache component based on variousload balancing or load sharing algorithms. Still further, the DNS servercomponents can utilize network performance metrics or measurements toassign specific resource cache components. Yet further, the DNS servercomponents can select a resource cache component based on routinginformation for a class of the requesting client computing device asdescribed in reference to FIG. 4. Again, the IP address selected by aDNS server component may correspond to a specific caching server in theresource cache. Alternatively, the IP address can correspond to ahardware/software selection component (such as a load balancer).

With reference now to FIG. 6, in an illustrative example, assume thatthe DNS server component 130 has selected the resource cache component132 of POP 128. Upon receipt of the IP address for the resource cachecomponent 132, the client computing device 102 transmits requests forthe requested content to the resource cache component 132. The resourcecache component 132 processes the request in a manner described aboveand the requested content is transmitted to the client computing device102.

With reference now to FIG. 7, one embodiment of a routine 700implemented by the CDN service provider 106 for processing a resourcerequest will be described. One skilled in the relevant art willappreciate that actions/steps outlined for routine 700 may beimplemented by one or many computing devices/components that areassociated with the CDN service provider 106. Accordingly, routine 700has been logically associated as being generally performed by the CDNservice provider 106, and thus the following illustrative embodimentsshould not be construed as limiting.

Routine 700 can apply to embodiments described both in reference to FIG.4 and FIGS. 5A-5C. As such, routine 700 will first be described inreference to embodiments corresponding to selecting resource cachecomponents at DNS servers based on routing information for a class ofthe requesting client computing device, as generally described inreference to FIG. 4.

At block 702, one of the DNS server components 118, 124, 130 receives aDNS query corresponding to a resource identifier. As previouslydiscussed, the resource identifier can be a URL that has been embeddedin content requested by the client computing device 102 and previouslyprovided by the content provider 104. The DNS server determines a classof the requesting client associate with the DNS query at block 704. Asmentioned above, the class can, for example, correspond to a specificgeographic region to which the client computing device belongs or aninternet service provider for the client computing device. Such classinformation can be determined from the client directly (such asinformation provided by the client computing device or ISP) orindirectly (such as inferred through a client computing device's IPaddress). In an illustrative embodiment, the determination of class atblock 704 can specifically include associating the requesting clientcomputing device to a cluster of other client computing devices based ona variety of criteria. Such criteria can include geographic region andinternet service provider data, as mentioned above, in addition torouting path information, networking equipment, client sponsored servicelevel agreements, content provider service level agreements, and thelike.

At a decision block 706, a test is conducted to determine whether thecurrent DNS server is authoritative to resolve the DNS query. In anillustrative embodiment, the DNS server can determine whether it isauthoritative to resolve the DNS query if there are no CNAME recordscorresponding to the received resource identifier. In this illustrativeembodiment, there are no CNAME records. Accordingly, the routinecontinues at block 708 where, in general, the current DNS serverdetermines routing information for the determined class. Specifically,in an illustrative embodiment, the DNS server selects an appropriateresource cache component for providing content associated with theresource request based on routing information for the determined classof the client computing device. The DNS server then provides the IPaddress of the selected resource cache component to the client computingdevice.

In an illustrative embodiment, the routing information can be a list ofresource cache components that can service the content request for aparticular class of client computing devices. The DNS server can use avariety of logic to select a resource cache component from the list. Inone embodiment, a probability of selecting each resource cache componenton the list can be defined, and the DNS server selects a resource cachecomponent based on these probabilities. Accordingly, in thisillustrative embodiment, a DNS server will select a resource cachecomponent on a frequency corresponding to the determined probabilities.For example, the DNS server will most frequently select the resourcecache component with the highest probability of selection, but can also,at times, select a resource cache component with a lower probability ofselection. In this case, the probabilities correspond to anticipatedperformance of the selected computing device. As will be describedfurther below, the CDN service provider 106 can monitor performance ofdelivering requested resources to clients in a particular class andthereafter update the routing information (e.g., probabilities)accordingly. In another embodiment, the probabilities can correspond toload shedding or other network traffic mitigation. By periodicallyselecting a non-preferred resource cache component and monitoring itsperformance for the class, the CDN service provider 106 can thusdetermine if changes to the routing information for the class aredesirable.

It will be appreciated by one skilled in the relevant art that a numberof algorithms or selection logic can be used for selecting a resourcecache component to service the resource request from a particular classof client computing devices. For example, in addition to thefrequency-based reinforcement algorithm described above, the DNS servermay implement alternative reinforcement learning algorithms. Examples ofother reinforcement algorithms include, but are not limited to,algorithms such as State-Action-Reward-State-Action (SARSA), Q-learning,delayed Q-learning, and the like. Additionally, other machine learningapproaches, such as support vector machines, neural networks, Bayesianengines, etc. may be utilized in conjunction with a DNS server to selectthe appropriate resource cache component.

Next, embodiments in which routing information for a class of therequesting client computing device is used to select an appropriate DNSserver for processing the request will be described. In suchembodiments, routine 700 similarly commences at block 702 where one ofthe DNS server components 118, 124, 130 receives a DNS querycorresponding to a resource identifier. As described above, the DNSserver further determines a class of the requesting client computingdevice associated with the DNS query at block 704.

At decision block 706, a test is conducted to determine whether thecurrent DNS server is authoritative to resolve the DNS query. In anillustrative embodiment, the DNS server can determine whether it isauthoritative to resolve the DNS query if there are no CNAME recordscorresponding to the received resource identifier. Alternative oradditional methodologies may also be practiced to determine whether theDNS server is authoritative.

If the current DNS server is authoritative (including a determinationthat the same DNS server will be authoritative for subsequent DNSqueries), the current DNS server resolves the DNS query by returning theIP address of cache server component. In a non-limiting manner, a numberof methodologies for selecting an appropriate resource cache componenthave been previously discussed. Additionally, as described above, the IPaddress may correspond to a specific cache server of a resource cachecomponent or generally to group of cache servers.

Alternatively, if at decision block 704 the DNS server is notauthoritative, at block 708, the DNS server component selects andtransmits an alternative resource identifier. As described above, theDNS server component can utilize a data store to identify a set ofpotential candidate CNAMES as a function of the current DNS query. TheDNS server then, either directly or via a network-based service, selectsone of the CNAME records defined in the data store as more appropriaterouting information based on logic that factors a determined class ofthe requesting client computing device. At block 710, different DNSserver components 118, 124, 130 receive a DNS query corresponding to theCNAME. The routine 700 then returns to decision block 704 and continuesto repeat as appropriate.

In an illustrative embodiment, where the DNS server is notauthoritative, the routing information can be a set or list of potentialcandidate CNAMES which correspond to one or more DNS servers that canservice the content request for a particular class of client computingdevices. Similar to selecting a cache resource component as describedabove, the DNS server can use a variety of logic to select a CNAME, oranother DNS server, from the list. In one embodiment, a probability ofselecting each CNAME in the set can be initially defined in a number ofways, and the DNS server selects a CNAME based on the definedprobabilities. Accordingly, in this illustrative embodiment, a DNSserver will most frequently select the CNAME with the highestprobability of selection, but can also, at times, select a CNAME with alower probability of selection. In this case, the probabilitiescorrespond to anticipated performance of the corresponding computingdevice. As will be described further below, the CDN service provider 106can monitor performance of delivering requested resources to clients ina particular class and thereafter update the probabilities. Again, infurther embodiments, the probabilities can correspond to load sheddingor other network traffic mitigation. By periodically selecting anon-preferred CNAME and monitoring performance of the corresponding DNSserver for the class, the CDN service provider 106 can thus determine ifchanges to the routing information for the class are desirable. It willbe appreciated by one skilled in the relevant art that a number ofalgorithms or selection logic can be used for selecting a CNAME/DNSserver to service the resource request from a particular class of clientcomputing devices.

With reference now to FIG. 8, one embodiment of a request routingroutine 800 for updating routing information will be described. Oneskilled in the relevant art will appreciate that actions/steps outlinedfor routine 800 may be implemented by one or many computingdevices/components that are associated with the CDN service provider106. Accordingly, routine 800 has been logically associated as beingperformed by the CDN service provider 106.

At a block 802, a first DNS server of the CDN service provider 106receives a DNS query corresponding to a requested resource from a clientcomputing device. As similarly described above in reference to block 704of FIG. 7, the DNS server at block 804 determines a class correspondingto the requesting client and associated with the DNS query. Also atblock 804, the DNS server determines either DNS or cache routinginformation based on the determined class of the client computing deviceas similarly described above. The routine 800 continues at block 806where network performance criteria associated with delivery of therequested resource is monitored. The network performance criteria cancorrespond to measurements of network performance for transmitting datafrom the CDN service provider POPs to the client computing device 102.In one embodiment, network data transfer latencies associated with thedelivery of the requested resource are measured by the client computingdevice 102. Alternatively, the CDN service provider 106, such as throughthe resource cache component, can measure the performance as part ofproviding content to a client computing device. Such network performancedata can be managed and maintained globally by the CDN service providerand shared with the DNS servers of the CDN or individually by the DNSservers of the CDN service provider. Moreover, network performancecriteria can be provided as a batch process from POPs or sent inresponse to a request from one POP to another.

With continued reference to FIG. 8, at a test block 808, a determinationis made as to whether an update to the routing information for theidentified class is needed based on the performance data. In oneembodiment, the update determination can be made by the CDN serviceprovider globally or by the individual DNS service components or DNSservers. In an illustrative embodiment where individual DNS serversdetermine whether to update routing information for a class, each DNSserver can manage and maintain routing information for the identifiedclass unique to the particular DNS server. In this illustrativeembodiment, the performance data can be maintained globally by the CDNservice provider and shared with the DNS components and/or DNS servers,with each DNS component and/or DNS server managing how the performancedata is used. Accordingly, routing information for a class may vary fromone DNS component/server to another.

Returning to FIG. 8, if an update is needed, the routing information forthe identified class is modified at block 810. In one embodiment, theCDN service provider 106 modifies a list of computing devices (e.g. DNScomponents/servers and/or resource cache components) for servicing aresource request from a particular class of client computing devices102. In another embodiment, the CDN service provider and/or specific DNScomponents/servers can maintain and modify probabilities of selection ofparticular computing devices for servicing a resource request for aclass of client computing devices. For example, if performance dataindicates that a DNS server and/or a resource cache component which hasa lower probability of selection has performed well, the probability ofselection may be increased so that the particular DNS server and/orresource cache component will be selected more frequently for servicinga resource request from a client computing device. After a modificationhas been made at block 810, or if an update is not needed at block 808,the routine 800 returns to block 802 for further processing as describedabove.

It will be appreciated by one skilled in the relevant art that there area number of ways to modify the routing information associated withrequests from a class of client computing devices. It will further beappreciated by one skilled in the relevant art that the timing at whichperformance is monitored and updates to routing information are made canvary.

It will be appreciated by those skilled in the art and others that allof the functions described in this disclosure may be embodied insoftware executed by one or more processors of the disclosed componentsand mobile communication devices. The software may be persistentlystored in any type of non-volatile storage.

Conditional language, such as, among others, “can,” “could,” “might,” or“may,” unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or without userinput or prompting, whether these features, elements and/or steps areincluded or are to be performed in any particular embodiment.

Any process descriptions, elements, or blocks in the flow diagramsdescribed herein and/or depicted in the attached FIGURES should beunderstood as potentially representing modules, segments, or portions ofcode which include one or more executable instructions for implementingspecific logical functions or steps in the process. Alternateimplementations are included within the scope of the embodimentsdescribed herein in which elements or functions may be deleted, executedout of order from that shown or discussed, including substantiallyconcurrently or in reverse order, depending on the functionalityinvolved, as would be understood by those skilled in the art. It willfurther be appreciated that the data and/or components described abovemay be stored on a computer-readable medium and loaded into memory ofthe computing device using a drive mechanism associated with a computerreadable storing the computer executable components such as a CD-ROM,DVD-ROM, or network interface further, the component and/or data can beincluded in a single device or distributed in any manner. Accordingly,general purpose computing devices may be configured to implement theprocesses, algorithms and methodology of the present disclosure with theprocessing and/or execution of the various data and/or componentsdescribed above.

It should be emphasized that many variations and modifications may bemade to the above-described embodiments, the elements of which are to beunderstood as being among other acceptable examples. All suchmodifications and variations are intended to be included herein withinthe scope of this disclosure and protected by the following claims.

What is claimed is:
 1. A computer-implemented method comprising:obtaining a first Domain Name System (DNS) query from a client computingdevice at a first DNS server, wherein the first DNS query is associatedwith a requested resource and wherein the first DNS server is associatedwith a content delivery network (CDN) service; determining a class ofthe client computing device associated with the first DNS query;determining an alternative resource identifier based on a probability ofselection for each alternative resource identifier identified in routinginformation for the class, wherein the alternative resource identifierincludes information for causing a second DNS query to resolve to adomain associated with the CDN service; and causing transmission of thealternative resource identifier to the client computing device inresponse to the first DNS query.
 2. The computer-implemented method asrecited in claim 1, wherein the alternative resource identifiercomprises a canonical name record identifier.
 3. Thecomputer-implemented method as recited in claim 1, wherein thealternative resource identifier comprises a uniform resource locator(URL).
 4. The computer-implemented method as recited in claim 3, whereinthe class is identified in the URL.
 5. The computer-implemented methodas recited in claim 3, wherein the class is identified in a DNS portionof the URL.
 6. The computer-implemented method as recited in claim 1further comprising: obtaining the second DNS query from the clientcomputing device at a second DNS server, wherein the second DNS serveris associated with the CDN service; and routing the second DNS querybased on routing information for the class.
 7. The computer-implementedmethod as recited in claim 1 further comprising: obtaining the secondDNS query from the client computing device at a second DNS server,wherein the second DNS server is associated with the CDN service;resolving the second DNS query to identify a cache component forproviding the requested resource; and causing transmission ofinformation identifying the cache component to the client computingdevice.
 8. A system comprising: a first network point of presence (POP)of a content delivery network (CDN) service, wherein the first networkPOP includes a first Domain Name System (DNS) server that receives afirst DNS query from a client computing device, wherein the first DNSquery is associated with a requested resource, and wherein the first DNSserver in the first network POP is associated with a memory andoperative for: determining a class of the client computing deviceassociated with the first DNS query; determining an alternative resourceidentifier based on probabilities of selection of alternative resourceidentifiers for the class, wherein the alternative resource identifierincludes information for causing a second DNS query to resolve to adomain of the CDN service; and causing transmission of the alternativeresource identifier to the client computing device in response to thefirst DNS query.
 9. The system as recited in claim 8, wherein thealternative resource identifier comprises a uniform resource locator(URL).
 10. The system as recited in claim 9, wherein the class isidentified in the URL.
 11. The system as recited in claim 9, wherein theclass is identified in a DNS portion of the URL.
 12. The system of claim8 further comprising: a second POP associated with the CDN service,wherein the second network POP includes a second DNS server thatreceives the second DNS query from the client computing device andwherein the second DNS server in the second network POP is associatedwith a memory and operative for: routing the second DNS query based onthe class.
 13. The system as recited in claim 8 further comprising: asecond POP associated with the CDN service, wherein the second networkPOP includes a second DNS server that receives the second DNS query fromthe client computing device and wherein the second DNS server in thesecond network POP is associated with a memory and operative for:resolving the second DNS query to identify a cache component forproviding the requested resource; and causing transmission ofinformation identifying the cache component to the client computingdevice.
 14. The system as recited in claim 8 further comprising a secondPOP associated with the CDN service, wherein the second network POPincludes a second DNS server that receives the second DNS query from theclient computing device and wherein the second DNS server in the secondnetwork POP is associated with a memory and operative for: determining asecond alternative resource identifier that includes information forcausing a third DNS query to resolve to a domain of the CDN service; andcausing transmission of the second alternative resource identifier tothe client computing device in response to the second DNS query.
 15. Asystem comprising: a first network point of presence (POP) of a contentdelivery network (CDN) service, wherein the first network POP includes afirst Domain Name System (DNS) server that receives a first DNS queryfrom a client computing device, wherein the first DNS query isassociated with a requested resource, and wherein the first DNS serverin the first network POP is associated with a memory and operative for:determining a class of the client computing device associated with thefirst DNS query; determining an alternative resource identifier based ona probability of selection of the alternative resource identifier forthe class, wherein the alternative resource identifier includesinformation for causing a second DNS query to resolve to a domain of theCDN service; and causing transmission of the alternative resourceidentifier to the client computing device in response to the first DNSquery.
 16. The system as recited in claim 15, wherein the class isassociated with a plurality of alternative resource identifiers eachhaving a probability of selection for the class.
 17. A systemcomprising: a first network point of presence (POP) of a contentdelivery network (CDN) service, wherein the first network POP includes afirst Domain Name System (DNS) server that receives a first DNS queryfrom a client computing device, wherein the first DNS query isassociated with a requested resource, and wherein the first DNS serverin the first network POP is associated with a memory and operative for:determining a class of the client computing device associated with thefirst DNS query, wherein the class is determined by identifying classinformation from a DNS portion of a uniform resource locator (URL)corresponding to the first DNS query; determining an alternative URL ofthe CDN service based on the class; and causing transmission of thealternative URL to the client computing device in response to the firstDNS query.
 18. The system as recited in claim 17, wherein determining analternative URL of the CDN service based on the class comprisesdetermining an alternative URL based on probabilities of selection ofalternative resource identifiers for the class.
 19. The system asrecited in claim 17, wherein determining an alternative URL of the CDNservice based on the class comprises determining an alternative URLbased on a probability of selection of the URL for the class.
 20. Thesystem as recited in claim 17, wherein determining an alternative URL ofthe CDN service based on the class comprises determining an alternativeURL based on a probability of selection for each alternative URLidentified in routing information for the class.